Houston: Superstorm Sandy, that has claimed many lives and wrecked havoc in the densely populated US East coast region, looks enormous even when seen from space, Indian-American astronaut Sunita Williams has said as she prepared to add to her record-setting space walking sojourns.

Williams is gearing up for another space walk scheduled for on Thursday to find and repair an ammonia coolant leak at the International Space Station (ISS).

"The superstorm that has been ravaging the East Coast is enormous, even when seen from space", Williams, commander of the International Space Station, said on Tuesday.

Williams said that she and her crew were able to make out the big swirl at the centre of Sandy as it neared land on Monday.

The cloud cover stretched from the Atlantic almost all the way to Chicago.

"It's pretty huge and hope everybody down there is safe and sound," Williams said

On Thursday, Williams will add to her record of the world's most experienced spacewalking woman. She and a crewmate will venture out on a spacewalk to find and repair an ammonia coolant leak on the ISS.

The leak is tiny, the equivalent to a hole about the diameter of a human hair.

But if it is not bypassed or repaired, the coolant in the channel 2B solar array will drop below safety margins over the next few months, taking down a critical power channel.

In a bid to locate the leak, Expedition 34 commander Williams and Japanese astronaut Akihiko Hoshide will suit up and venture outside the station to operate a valve and reconfigure coolant lines, isolating the part of the channel 2B coolant loop that snakes through a large folding radiator.

Then they will deploy a spare radiator used during the early stages of space station assembly and route the channel 2B coolant through the older panel.

If the leak ultimately goes away -- and it likely it will take several weeks to find out -- engineers will know the problem was in the original radiator, most likely the result of a space debris impact.

In that case, station managers could opt to use the older radiator indefinitely, solving the problem.

If the leak continues, however, they would have to consider replacing a pump module or taking more extensive steps in a future spacewalk.

But they will have more time to consider their options.

The old radiator has ammonia of its own to contribute and using it will effectively top off the system, keeping the coolant equipment operating for another year or so, assuming no other problems arise.

"What this (spacewalk) will tell us is whether the radiator is the cause of the leak," said space station Programme Manager Mike Suffredini.

"If it turns out the leak continues, we have a little time. When we filled this system a year ago, the result of that fill was to also fill the early ammonia system as well, so we have extra ammonia in that loop," Suffredini said.

"So it buys us a little time. It lets us isolate the PVR to see if that's the cause. If that turns out not to be the cause, then we have to think about the next steps," he added.

Williams is also set to enjoy Halloween in space, as she is going to trick the crew by wearing a surprise costume and dressing her stuffed dog as --dracula.

She's challenged her crewmates to scrounge up costumes. And while the six people onboard the International Space Station (ISS) won't be visited by any candy seekers on Wednesday, a Russian spacecraft will perform a "trick" to possibly deliver treats for the crew.

The six space station residents, two Americans, three Russians and one Japanese, expect to get a special Halloween visitor.

A Russian supply ship is scheduled to blast off from Kazakhstan this morning and, in an unusually short transit, arrive at the orbiting lab several hours later.